public class demo1 {
    int a = 100;

    public void gengGai (int a) {
        this.a=200;
        System.out.println("修改成功");
    }

    public static void main(String[] args) {
        demo1 demo = new demo1();
        demo.gengGai(300);
        System.out.println(demo.a);
    }
}
